VACANCY levels for registered nurses pose the biggest risk to the successful introduction of safe staffing levels on Wales' hospital wards, a nursing chief has warned.

Wales has led the way in enshrining in law the principle of safe nurse staffing levels on wards, and these are meant to be set and implemented from April 6 next year.

But with nurse recruitment and retention an issue across Wales and much of the rest of the UK, vacancy numbers could make ensuring safe staffing levels - and the balance of qualified and unqualified staff on wards - difficult to achieve and maintain.

"It is our biggest risk, and others have the same issue," said Bronagh Scott, nursing director at Aneurin Bevan University Health Board, which has approaching 260 nursing posts unfilled.

"I think it (the legislation) is a good thing, but it will create challenges for health boards."

Guidance on implementing the Nurse Staffing Levels (Wales) Act focuses on acute adult inpatients medical and surgical wards. Assessments aretaking place, and this is set to apply to almost 30 wards at the Royal Gwent and Nevill Hall Hospitals. Consideration is also being given to some wards at Ysbyty Ystrad Fawr in Ystrad Mynach.

Ms Scott added that wards will not need the same number of nurses, even if they have the same number of patients, as much will depend on the care the patients need. Evidence-based assessment and "the professional expertise and judgement of those looking after the patients" will help determine what those safe levels are.